1. Field of the Invention
The present invention relates to a slider having a magnetic head installed thereon and floating at a predetermined height above a recording medium and, more particularly, to a negative pressure air bearing slider which maintains a stable float state by concurrently generating positive pressure and negative pressure.
2. Description of the Related Art
Magnetic recording/reproducing apparatuses such as hard disk drives include magnetic heads for recording and reproducing magnetic signals on and from a recording medium. As shown in FIG. 1, a magnetic head 10 is installed at a slider 20 provided at one end of a swing arm 30. The magnetic head 10 moves to a desired track position above a disk (not shown) which is a recording medium as the swing arm 30 pivots, to perform recording or reproducing information.
In this case, the slider 20 staying on the surface of the disk begins lifting due to wind generated as the disk rotates. Since an end portion of the swing arm 30 where the slider 20 is installed is elastically biased toward the surface of the disk, when the disk stops rotating, the slider 20 lands on the surface of the disk.
The slider 20 can be lifted due to the pressure by the air entering between the surface of the disk and the slider 20 during the rotation of the disk with respect to the slider 20. Since the air entering between the surface of the disk and the slider 20 during the rotation of the disk serves as a bearing, the slider 20 can be lifted and continuously float above the disk.
However, if only the positive pressure which lifts the slider 20 is continuously generated, the slider 20 is not maintained at the uniform height, but fluctuates unstably. Accordingly, a negative pressure bearing slider which generates negative pressure to pull the slider 20 toward the surface of the disk, concurrently with positive pressure, is widely adopted.
FIG. 2 shows the negative pressure air bearing slider 20. As shown in the drawing, a plurality of rails 22, 23 and 24 for generating positive pressure and negative pressure by air are provided at the slider 20. Two front rails 22 are arranged at the front side of the slider 20 where air enters, forming an air inlet passage 21 interposed therebetween. A negative pressure rail 23 having a boomerang shape is formed at the rear side of the slider 20. Space 28 formed between the front rails 22 and the negative pressure rail 23 is for generating positive pressure. Since the air inlet passage 21 between two front rails 22 is wider than each of air outlet passages 26 through which air is exhausted along the negative pressure rail 23, the air stays in the space 28. Thus, as the air is accumulated in the positive pressure space 28, the pressure increases and affects the slider 20. Reference numeral 24 denotes a rear rail where a magnetic head 27 is installed. Negative pressure space 25 is formed between both wings of the boomerang-shaped negative pressure rail 23. The air in the negative pressure space 25 is exhausted together with air entering from the front side of the slider 20, passing above the negative pressure space 25, and exhausted toward the rear side of the slider 20. However, since the negative pressure rail 23 serves as a barrier for entering of air from the front side, new air is difficult to enter the negative pressure space 25. Thus, negative pressure is generated in the negative pressure space 25. The horizontal surfaces of the rails 22, 23 and 24 contribute to the generation of positive pressure. Consequently, the positive pressure generated by the positive pressure space 28 and the horizontal surfaces of the rails 22, 23 and 24 and the negative pressure generated by the negative pressure space 25 make the slider 20 float at a predetermined height in a balanced state.
As shown in FIG. 3, an angle made by the lengthwise direction of the slider 20 and the tangential direction of a track t of a disk D is referred to as a skew angle xcex8. Since the swing arm 30 pivots around a pivot shaft as shown in the drawing, the skew angle cannot be maintained to be zero (0) at all tracks. When the skew angle xcex8 occurs, since the slider 20 is not disposed to be symmetrical with respect to the input air, the amount of the air entering through the air inlet passage 21 and exhausted through the air exhaust passage 26 is much greater than that of the air passing above the negative pressure space 25. That is, when the skew angle xcex8 is 0, the air entering the air inlet passage 21 is accurately collided with the middle portion of the negative pressure rail 23 and passes above the negative pressure space 25. Otherwise, after colliding with the negative pressure space 25, most air is exhausted through the air exhaust passages 26. Then, since the flow of air which will take the air in the negative pressure space 25 becomes weak, so that the negative pressure in the negative pressure space 25 is lowered, the floating height of the slider 20 cannot be stably maintained. Furthermore, since the flow of air toward the rear rail 24 where the magnetic head 27 is installed is not smooth, the positive pressure of the rear rail 24 is lowered so that the slider 20 floats unstably.
When the air exhaust passage 26 is narrowed by making the horizontal surface of the negative pressure rail 23 large, to solve the above problem, although the amount of air exhausted through the air exhaust passage can be reduced, since the area contacting the disk increases, the slider 20 can be easily damaged due to friction with the disk when the disk begins and ends rotation. Thus, a slider having an improved structure which can prevent the exhaust of air in a large amount through the air exhaust passage, without increasing the contact area with the disk, is needed.
To solve the above problems, it is an object of the present invention to provide a negative pressure bearing slider having an improved structure so that the exhaust of air in a large amount through an air exhaust passage can be effectively reduced.
Accordingly, to achieve the above object, there is provided a negative pressure air bearing slider comprising a pair of front rails having a predetermined air inlet passage interposed therebetween at a front side of the slider where air enters, a negative pressure rail disposed at a rear of the front rails and forming air outlet passages connected to the air inlet passage, and forming a negative pressure space where negative pressure is generated according to a flow of air at a rear thereof, and a rear rail disposed at the rear of the negative pressure space, where a magnetic head is installed, in which a stepped portion protruding toward the air outlet passages is formed at the negative pressure rail.